Device and method for carrying out a two-stage linear movement

Abstract

A device for carrying out a two-stage, linear movement as well as an associated method for displacing a displaceable structural unit relative to a stationary structural unit. A first drive unit drives a shaft, which is in operative connection with a tube, which is connected to the displaceable structural unit. If a predeterminable condition is substantially achieved, a switch is made from the first drive unit to a second drive unit. Because the tube extends through the stationary structural unit and is displaced relative to the stationary structural unit when the first drive unit is actuated, the at least one separating means being jointly displaceable with the second drive unit and coupling in a detachable manner the tube to the second drive unit initially when the condition is achieved and thereby separating the shaft from the flow of force, as soon as the second drive unit is actuated alone, the members, which transfer the rotary movement into a straight movement, can be protected in a two-stage linear movement.

What is claimed is:  
     
       1. Device for carrying out a substantially two-stage linear movement comprising: 
       a stationary structural unit;  
       a displaceable structural unit;  
       at least one first electromechanical drive unit mounted on the stationary structural unit;  
       at least one shaft rotatably driven by the first drive unit and having a region with external thread;  
       at least one tube with internal thread, which tube is disposed coaxially relative to the respective shaft, is displaced with the displaceable structural unit and is in operative connection with the external thread for the displacement of the displaceable structural unit;  
       separating means for a separation of the shaft at least from a further flow of force when at least one predeterminable condition is obtained, the predeterminable condition includes at least one of a translatory position of the tube and a predeterminable axial force;  
       at least one second drive unit, which is actuatable once the predeterminable condition has been achieved,  
       wherein the tube extends through the stationary structural unit and is displaced relative to the stationary structural unit when the first drive unit is actuated, the separating means being jointly displaceable with the second drive unit and, when the predeterminable condition is achieved, the tube is firstly coupled in a detachable manner to the second drive unit and in so doing separates the shaft at least from the further flow of force, which is produced by the second drive unit, as soon as the second drive unit is actuated alone, and that the separating means works radially on the tube.  
     
     
       2. Device according to  claim 1 , wherein the separating means is actively actuatable through impingement of associated cylinder areas. 
     
     
       3. Device according to  claim 1 , wherein the separating means is actively actuatable in a magnetic manner. 
     
     
       4. Device according to  claim 1 , wherein the separating means friction-lock the tube in a central manner once the predetermined condition has been obtained. 
     
     
       5. Device according to  claim 1 , wherein the second hydraulic drive unit has as piston a rotary piston that surrounds the tube coaxially and a cylinder of which is formed through a recess in the stationary structural unit. 
     
     
       6. Device according to  claim 5 , wherein the cylinder areas of the second drive unit are defined in a direction of the rotary piston by a base of the recess and by an annular flange, which is mounted on the stationary structural unit. 
     
     
       7. Device according to  claim 1 , wherein to obtain a superposed displacement, the first drive unit and the second drive unit are actuatable simultaneously at least at times. 
     
     
       8. Device according to  claim 1 , wherein the separating means is configured as a hydraulically or magnetically actuatable tension clamp. 
     
     
       9. Device according to  claim 1 , wherein the separating means is configured as a hydraulically or magnetically actuatable tension clamp, wherein the second hydraulic drive unit has a first rotary piston, and wherein the tension clamp is formed by a collet having a first cone that interacts with a second cone of a second rotary piston, the second rotary piston is mounted in the first rotary piston, the collet is mounted on a flange of the second rotary piston and the flange extends along the tube. 
     
     
       10. Device according to  claim 1 , wherein the separating means is formed by a hydraulic clamping sleeve. 
     
     
       11. Device according to  claim 1 , wherein a mounting of the shaft is supported on the first drive unit in a resilient manner via cup springs. 
     
     
       12. Device according to  claim 1 , wherein the first drive unit is supported on a side of the stationary structural unit remote from the displaceable structural unit. 
     
     
       13. Device according to  claim 1 , wherein the first drive unit is supported on the stationary structural unit via connecting means in such a manner that a head of the shaft, which bears the external thread, is disposed approximately in an opening of the stationary structural unit. 
     
     
       14. Device according to  claim 13 , wherein the separating means, which work radially on the tube, is at a spacing from the head in the axial direction of the tube. 
     
     
       15. Device according to  claim 1 , wherein the stationary structural unit is a supporting member of a substantially two-stage, linear closing unit on a plastics injection molding machine and the displaceable structural unit is the displaceable mold carrier of a plastics injection molding machine. 
     
     
       16. Device according to  claim 1 , wherein the first drive unit is a portion of a magnetically operated linear motor being in operative connection with the tube. 
     
     
       17. Device according to  claim 1 , wherein the separating means, when actuated once the predeterminable condition has been obtained, secure the tube to an intermediate member and in that the intermediate member is displaceable in a closing direction at least by means or magnetic attractive forces produced by the second drive unit to provide a closing force in the closing direction (s-s). 
     
     
       18. Method for performing a substantially two-stage, linear movement, the method comprising: 
       actuating a shaft by means of at least of a first electromechanical drive unit until a predeterminable condition is obtained, the first electromechanical drive unit is mounted on a stationary structural unit;  
       separating the shaft at least from the further flow of force, when the predeterminable condition is achieved, by separating means that work radially on the tube;  
       actuating at least a second drive unit once the predeterminable condition has been achieved, for a displacement of the displaceable structural unit via at the tube, which is disposed coaxially relative to the respective shaft, which is displaced with the displaceable structural unit and is in operative connection with the shaft; and  
       displacing the tube relative to the stationary structural unit when the first drive unit is actuated, the separating means being jointly displaceable with the second drive unit, and when the predeterminable condition is achieved, the tube is firstly coupled in a detachable manner to the second drive unit and in doing so separates the shaft at least from the further flow of force produced by the second drive unit, as soon as the second drive unit is actuated alone.  
     
     
       19. Method according to  claim 18 , wherein the separating means is actively connected through impingement of associated cylinder areas or respectively is actively connected in a magnetic manner. 
     
     
       20. Method according to  claim 18 , wherein the separating means friction-lock the tube in a central manner once the predeterminable condition is achieved. 
     
     
       21. Method according to  claim 18 , wherein to obtain a superposed displacement, the first drive unit and the second drive unit are actuated simultaneously at least at times. 
     
     
       22. Device according to  claim 1 , further comprising rolling bodies disposed between the shaft and the tube and retained so as to be non-displaceable in an axial manner opposite the shaft. 
     
     
       23. Device for carrying out a substantially two-stage linear movement comprising: 
       a stationary structural unit;  
       a displaceable structural unit;  
       at least one shaft having a region with external thread;  
       at least one first drive unit mounted on the stationary structural unit, the first drive unit produces a force on the shaft so that the shaft is rotatably driven by the first drive unit;  
       at least one tube with internal thread, which tube is disposed coaxially relative to the shaft, is displaced with the displaceable structural unit and is in operative connection with the external thread for the displacement of the displaceable structural unit;  
       separating means for a separation of the shaft at least from a further flow of force when at least one predeterminable condition is obtained, the predeterminable condition includes at least one of a translatory position of the tube and a predeterminable axial force;  
       at least one second drive unit, which is actuatable once the predeterminable condition has been achieved,  
       wherein the tube extends through the stationary structural unit and is displaced relative to the stationary structural unit when the first drive unit is actuated, the separating means being jointly displaceable with the second drive unit and, when the predeterminable condition is achieved, the tube is firstly coupled in a detachable manner to the second drive unit and in so doing separates the shaft at least from the further flow of force, which is produced by the second drive unit, as soon as the second drive unit is actuated alone, and that the separating means works radially on the tube.  
     
     
       24. Device for carrying out a substantially two-stage linear movement comprising: 
       a stationary structural unit;  
       a displaceable structural unit;  
       at least one first electromechanical drive unit mounted on the stationary structural unit;  
       at least one shaft rotatably driven by the first drive unit and having a region with external thread;  
       at least one tube with internal thread, which tube is disposed coaxially relative to the respective shaft, is displaced with the displaceable structural unit and is in operative connection with the external thread for the displacement of the displaceable structural unit;  
       separating means for a separation of the shaft at least from a further flow of force when at least one predeterminable condition is obtained, the predeterminable condition includes at least one of a translatory position of the tube and a predeterminable axial force;  
       at least one second drive unit, which is actuatable once the predeterminable condition has been achieved,  
       wherein the tube extends through the stationary structural unit and is displaced relative to the stationary structural unit when the first drive unit is actuated, the separating means being jointly displaceable with the second drive unit and, when the predeterminable condition is achieved, the tube is firstly coupled in a detachable manner to the second drive unit and in so doing separates the shaft at least from the further flow of force, which is produced by the second drive unit, as soon as the second drive unit is actuated alone, and that the separating means works radially on the tube, and  
       wherein the separating means is configured as a hydraulically or magnetically actuatable tension clamp and  
       wherein the separating means is formed by a hydraulic clamping sleeve.